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LED picture backlighting circuit

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John Rudd:

--- Quote from: awemawson on January 13, 2014, 04:05:23 AM ---OK Chris here is an "Off the Wall" suggestion - pun intended  :lol:

In many parts of the uk you are near enough to a reasonably powered transmitter to draw a few milliamps from a circuit tuned to the right frequency. Just a simple coil and parallel capacitor, diode rectification and you have a micro power source.

Andrew

--- End quote ---

The basis of the crystal radio.......who'd have thought it?.....

John Swift:
Hi John

thats an idea if you live near this :-

http://en.wikipedia.org/wiki/Droitwich_Transmitting_Station

or  you can use this circuit to step up a single cell's output :-

http://en.wikipedia.org/wiki/Joule_thief
or
http://www.madscientisthut.com/pdf/JT_Kit011AOW_assembly_instructions.pdf

    John

John Rudd:
Ummm.... How about the tuned circuit followed by a charge pump circuit to lift the voltage?

John Swift:

yes , but the joule thief will look brighter for the same power

2A for 1% of the time will look brighter than 20 mA for 100%
due to the way the eye responds to the intense pulses of light
I'll have to look closer at the data sheet to check the maximum current and pulse width


  John

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